scholarly journals BAECC: A Field Campaign to Elucidate the Impact of Biogenic Aerosols on Clouds and Climate

2016 ◽  
Vol 97 (10) ◽  
pp. 1909-1928 ◽  
Author(s):  
Tuukka Petäjä ◽  
Ewan J. O’Connor ◽  
Dmitri Moisseev ◽  
Victoria A. Sinclair ◽  
Antti J. Manninen ◽  
...  
Keyword(s):  
Atmospheric Aerosols ◽  
Numerical Models ◽  
Cloud Formation ◽  
In Situ Observation ◽  
Forest Environment ◽  
Surface Precipitation ◽  
Biogenic Aerosols ◽  
Boreal Environment ◽  
The Impact

Abstract During Biogenic Aerosols—Effects on Clouds and Climate (BAECC), the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program deployed the Second ARM Mobile Facility (AMF2) to Hyytiälä, Finland, for an 8-month intensive measurement campaign from February to September 2014. The primary research goal is to understand the role of biogenic aerosols in cloud formation. Hyytiälä is host to the Station for Measuring Ecosystem–Atmosphere Relations II (SMEAR II), one of the world’s most comprehensive surface in situ observation sites in a boreal forest environment. The station has been measuring atmospheric aerosols, biogenic emissions, and an extensive suite of parameters relevant to atmosphere–biosphere interactions continuously since 1996. Combining vertical profiles from AMF2 with surface-based in situ SMEAR II observations allows the processes at the surface to be directly related to processes occurring throughout the entire tropospheric column. Together with the inclusion of extensive surface precipitation measurements and intensive observation periods involving aircraft flights and novel radiosonde launches, the complementary observations provide a unique opportunity for investigating aerosol–cloud interactions and cloud-to-precipitation processes in a boreal environment. The BAECC dataset provides opportunities for evaluating and improving models of aerosol sources and transport, cloud microphysical processes, and boundary layer structures. In addition, numerical models are being used to bridge the gap between surface-based and tropospheric observations.

scholarly journals Horizontally Oriented Plates in Clouds

2004 ◽  
Vol 61 (23) ◽  
pp. 2888-2898 ◽  
Author(s):  
François-Marie Bréon ◽  
Bérengère Dubrulle
Keyword(s):  
Atmospheric Turbulence ◽  
Tilt Angle ◽  
Signal Amplitude ◽  
In Situ Observation ◽  
Horizontal Plate ◽  
Specular Reflectance ◽  
Aerodynamic Model ◽  
The Earth ◽  
The Impact

Abstract Horizontally oriented plates in clouds generate a sharp specular reflectance signal in the glint direction, often referred to as “subsun.” This signal (amplitude and width) may be used to analyze the relative area fraction of oriented plates in the cloud-top layer and their characteristic tilt angle to the horizontal. Use is made of spaceborne measurements from the Polarization and Directionality of the Earth Reflectances (POLDER) instrument to provide a statistical analysis of these parameters. More than half of the clouds show a detectable maximum reflectance in the glint direction, although this maximum may be rather faint. The typical effective fraction (area weighted) of oriented plates in clouds lies between 10−3 and 10−2. For those oriented plates, the characteristic tilt angle is less than 1° in most cases. These low fractions imply that the impact of oriented plates on the cloud albedo is insignificant. The largest proportion of clouds with horizontally oriented plates is found in the range 500– 700 hPa, in agreement with typical in situ observation of plates in clouds. A simple aerodynamic model is proposed that accounts for the orienting torque of the flow as the plate falls under its own gravity and the disorienting effects of Brownian motion and atmospheric turbulence. The model indicates that the horizontal plate diameters are in the range 0.1 to a few millimeters. For such sizes, Brownian forces have a negligible impact on the plate orientation. On the other hand, typical levels of atmospheric turbulence lead to tilt angles that are similar to those estimated from the glint observation.

An Overview of Maritime Transportation Dynamics-Mobilization and Livelihood in Galápagos Islands

2021 ◽  
pp. 52-90
Author(s):  
María Belén Arteaga-Custode ◽  
Claudia Fernanda Betancourt-Ruiz ◽  
María Serena López-Donoso ◽  
Sophia Veronique Nieto-Vasco ◽  
Carolina Stefanía Pantoja-Cabrera ◽  
...  
Keyword(s):  
Relevant Information ◽  
Population Based ◽  
Galapagos Islands ◽  
Maritime Transportation ◽  
Floating Population ◽  
In Situ Observation ◽  
Galápagos Islands ◽  
The Impact ◽  
Official Sources

The Galápagos Islands are one of the biggest marine reserves in the world, home to a complex dynamic between its inhabitants, tourists, and biodiversity. Therefore, control over the logistics surrounding the resulting human mobilization process is fundamental to minimize the impact on the Islands' natural resources. This research gathers relevant information regarding the operation of the maritime transportation system of the islands and the waste management of its floating population based on official sources as well as in-situ observation. This chapter includes three sections with the purpose of maximizing the range of information analyzed. The first section covers the maritime cargo transportation from the continent to the islands. The second one covers the transportation of people between the islands, and the third covers the transportation and management of waste produced by each island. The information covers the institutions and policies that govern each of the systems considered and can serve to optimize the transportation logistics of the Galápagos Islands.

Analysis of the impact of biomass burning emissions on global ozone production in the upper troposphere with MOCAGE CTM and IAGOS airborne data.

2020 ◽  
Author(s):  
Martin Cussac ◽  
Virginie Marécal ◽  
Valérie Thouret ◽  
Béatrice Josse
Keyword(s):  
Significant Role ◽  
Biomass Burning ◽  
Transport Model ◽  
Chemical Species ◽  
Ozone Production ◽  
In Situ Observation ◽  
Transport Pathway ◽  
Upper Troposphere ◽  
The Impact

<p>The UTLS (Upper Troposphere/Lower Stratosphere) is a key layer of the atmosphere as its chemical composition impacts both the troposphere and the stratosphere, and therefore plays a significant role in the climate system. Ozone at this altitude for instance plays a great role on surface temperature. Unlike in the stratosphere; it can be produced from the photolysis of precursors originating in the troposphere; mainly nitrous oxides (NO<sub>x</sub>) and carbon monoxide (CO) at this pressure range. Biomass burning emissions in particular are likely to play a significant role in the quantities of these species in the upper troposphere and thus impacting ozone balance. This effect is investigated thanks to the global chemistry transport model MOCAGE. Because of the strong vertical gradients in this layer of the atmosphere, well resolved in-situ observation dataset are valuable for model evaluation. As of measurements used to validate MOCAGE results, IAGOS in-situ measurements from equipped commercial aircraft were chosen for their fine vertical resolution as well as their wide geographical coverage. Using both of these tools, upper tropospheric air composition is studied, with a focus on ozone precursors and production linked to biomass burning emissions.</p><p>Firstly is investigated the direct impact of biomass burning emissions on CO concentration in the upper troposphere, as it is both a good tracer of wildfire plumes in the atmosphere and it plays a role in the upper troposphere chemical balance. For this purpose MOCAGE simulations spaning over the year of 2013 where biomass burning emissions were turned on and off are compared to estimate a contribution to upper tropospheric CO. These simulations were validated using all the available data from the IAGOS database. It was found that biomass burning impacted CO levels globally, with the strongest enhancement happening above the most emitting areas (equatorial Africa and the Boreal forests). The importance of a fast vertical transport pathway above the fires was also highlighted with the possible occurrence of pyroconvection in addition to deep convection. Secondly, other chemical species related to ozone production were looked upon. Peroxyacetyl Nitrates (PAN) for instance were found to be impacted by biomass burning as it is a product of NOx oxidation as well as the main "reservoir" specie for NOx in the upper troposphere. Ultimately, ozone production resulting from biomass burning emissions is investigated, both in biomass burning plumes encountered by IAGOS aircraft, and on a more global scale using the MOCAGE simulations.</p>

scholarly journals Coupled Sea Ice–Ocean-State Estimation in the Labrador Sea and Baffin Bay

2013 ◽  
Vol 43 (5) ◽  
pp. 884-904 ◽  
Author(s):  
Ian Fenty ◽  
Patrick Heimbach
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Numerical Models ◽  
Labrador Sea ◽  
In Situ Observation ◽  
Quasi Equilibrium ◽  
Ocean Variability ◽  
The Relationship ◽  
Ice Model

Abstract Sea ice variability in the Labrador Sea is of climatic interest because of its relationship to deep convection, mode-water formation, and the North Atlantic atmospheric circulation. Historically, quantifying the relationship between sea ice and ocean variability has been difficult because of in situ observation paucity and technical challenges associated with synthesizing observations with numerical models. Here the relationship between ice and ocean variability is explored by analyzing new estimates of the ocean–ice state in the northwest North Atlantic. The estimates are syntheses of in situ and satellite hydrographic and ice data with a regional ⅓° coupled ocean–sea ice model. The synthesis of sea ice data is achieved with an improved adjoint of a thermodynamic ice model. Model and data are made consistent, in a least squares sense, by iteratively adjusting control variables, including ocean initial and lateral boundary conditions and the atmospheric state, to minimize an uncertainty-weighted model–data misfit cost function. The utility of the state estimate is demonstrated in an analysis of energy and buoyancy budgets in the marginal ice zone (MIZ). In mid-March the system achieves a state of quasi-equilibrium during which net ice growth and melt approaches zero; newly formed ice diverges from coastal areas and converges via wind and ocean forcing in the MIZ. The convergence of ice mass in the MIZ is ablated primarily by turbulent ocean–ice enthalpy fluxes. The primary source of the enthalpy required for sustained MIZ ice ablation is the sensible heat reservoir of the subtropical-origin subsurface waters.

scholarly journals The impact of mineral dust on cloud formation during the Saharan dust event in April 2014 over Europe

2018 ◽  
Author(s):  
Michael Weger ◽  
Bernd Heinold ◽  
Ina Tegen ◽  
Christa Engler ◽  
Patric Seifert ◽  
...  
Keyword(s):  
Cloud Cover ◽  
Mineral Dust ◽  
Dust Cloud ◽  
Ice Nucleation ◽  
Saharan Dust ◽  
Cloud Formation ◽  
Cirrus Cloud ◽  
Dust Event ◽  
The Impact

Abstract. A regional modeling study on the impact of desert dust on cloud formation is presented for a major Saharan dust outbreak over Europe from 2 April to 5 April 2014. The dust event coincided with an extensive and dense cirrus cloud layer, suggesting an influence of dust on atmospheric ice nucleation. Using interactive simulation with the regional dust model COSMO-MUSCAT, we investigate cloud and precipitation representation in the model and test the sensitivity of cloud parameters to dust-cloud and dust-radiation interactions of the simulated dust plume. We evaluate model results with ground-based and space-borne remote sensings of aerosol and cloud properties, as well as the in situ measurements obtained during the ML-CIRRUS aircraft campaign. A run of the model with single-moment bulk microphysics without online dust feedback considerably underestimated cirrus cloud cover over Germany in the comparison with infrared satellite imagery. This was also reflected in simulated upper-tropospheric ice water content (IWC), which accounted only for 20 % of the observed values. The interactive dust simulation with COSMO-MUSCAT, including a two-moment bulk microphysics scheme and dust-cloud as well as dust-radiation feedback, in contrast, led to significant improvements. The modeled cirrus cloud cover and IWC were by at least a factor of two higher in the relevant altitudes compared to the non-interactive model run. We attributed these improvements mainly to enhanced deposition freezing in response to the high mineral dust concentrations. This was corroborated further in a significant decrease in ice particle radii towards more realistic values, as compared to in situ measurements from the ML-CIRRUS aircraft campaign. By testing different empirical ice nucleation parameterizations, we further demonstrate that remaining uncertainties in the ice nucleating properties of mineral dust affect the model performance at least as significantly as to whether including the online representation of the mineral distribution. Dust-radiation interactions played a secondary role for cirrus cloud formation, but contributed to a more realistic representation of precipitation by suppressing moist convection in southern Germany. In addition, a too low specific humidity in the 7 to 10 km altitude range in the boundary conditions was identified as a main reason of misrepresentation of cirrus clouds in this model study.

scholarly journals In situ observation of the impact of hydrogen bubbles in Al–Cu melt on directional dendritic solidification

2021 ◽  
Vol 56 (13) ◽  
pp. 8225-8242
Author(s):  
T. Werner ◽  
M. Becker ◽  
J. Baumann ◽  
C. Pickmann ◽  
L. Sturz ◽  
...  
Keyword(s):  
Solidification Front ◽  
Bubble Diameter ◽  
Alloy System ◽  
Local Variation ◽  
Bubble Nucleation ◽  
In Situ Observation ◽  
Cu Alloy ◽  
Solidification Speed ◽  
The Impact

AbstractMuch research has already been focused on the solid-bubble interaction in the interdendritic space for solidifying materials. However, commonly, bubble nucleation is not limited to the mushy zone but also occurs in the liquid melt. In the present research on an Al-$$10 \, \%\mathrm {wt. \,}$$ 10 % wt . Cu alloy, the interaction between these bubbles and the approaching solidification front becomes apparent under in situ X-radiography and allows for new insights into the influence of bubbles on the solidifying microstructure. The observed effects comprise bulging of the solidification front toward the bubble, bending of dendrites in front of the bubble, coronal outgrowths surrounding the bubbles, as well as bubble growth, bubble pushing, and bubble eruption. It is found that for the present Al–Cu alloy, the local variation in the solidification speed can be attributed to the bubbles’ insulating properties. The range of this effect was observed to be up to $$900 \,\upmu \text {m}$$ 900 μ m , depending on the bubble diameter, locally increasing solidification speed by up to $$350 \, \%$$ 350 % . The influences of Marangoni vortices and coronal nucleation of misoriented dendrites around bubbles on the homogeneity of the microstructure are discussed. A comparison with experiments on model alloys and simulations from various other studies highlights the similarities and differences to this metallic alloy system.

scholarly journals Theoretical Study of Aerosols Loading and Retention Over Bolgatanga, Ghana

2017 ◽  
Vol 10 ◽  
pp. 117862211774699
Author(s):  
Emetere Moses E ◽  
Sanni SE ◽  
Akinwumi SA
Keyword(s):  
Atmospheric Aerosols ◽  
Regional Climate ◽  
Life Forms ◽  
Cloud Formation ◽  
Percentage Increase ◽  
Data Set ◽  
Depth Data ◽  
Negative Effect ◽  
The Impact ◽  
Aerosol Optical Depth Data

The aerosols loading and retention over West Africa have grave effect on life-forms through the impact on health, farming, rainfall pattern, cloud formation, and regional climate. Bolgatanga can be found on the latitude and longitude of 10.78°N and 0.85°W, respectively. This research is focused on an investigative consideration of the negative effect of atmospheric aerosols over Bolgatanga in Ghana through a conceptual model using analytical and descriptive statistical methods with MATLAB curve-fitting tool. The model was verified using aerosol optical depth data set from satellite imagery—multi-angle imaging specto-reflectometer (MISR)—obtained over a period of 13 years. The highest percentage increase of aerosol retention was 64.27% over the research site. The model was used to estimate the atmospheric constants as 0.67, tuning constants as 0.24, and phase difference as [Formula: see text]. The physical interpretation of the results was analyzed systematically.

scholarly journals The impact of mineral dust on cloud formation during the Saharan dust event in April 2014 over Europe

2018 ◽  
Vol 18 (23) ◽  
pp. 17545-17572 ◽  
Author(s):  
Michael Weger ◽  
Bernd Heinold ◽  
Christa Engler ◽  
Ulrich Schumann ◽  
Axel Seifert ◽  
...  
Keyword(s):  
Cloud Cover ◽  
Mineral Dust ◽  
Dust Cloud ◽  
Ice Nucleation ◽  
Saharan Dust ◽  
Cloud Formation ◽  
Cirrus Cloud ◽  
Dust Event ◽  
The Impact

Abstract. A regional modeling study on the impact of desert dust on cloud formation is presented for a major Saharan dust outbreak over Europe from 2 to 5 April 2014. The dust event coincided with an extensive and dense cirrus cloud layer, suggesting an influence of dust on atmospheric ice nucleation. Using interactive simulation with the regional dust model COSMO-MUSCAT, we investigate cloud and precipitation representation in the model and test the sensitivity of cloud parameters to dust–cloud and dust–radiation interactions of the simulated dust plume. We evaluate model results with ground-based and spaceborne remote sensing measurements of aerosol and cloud properties, as well as the in situ measurements obtained during the ML-CIRRUS aircraft campaign. A run of the model with single-moment bulk microphysics without online dust feedback considerably underestimated cirrus cloud cover over Germany in the comparison with infrared satellite imagery. This was also reflected in simulated upper-tropospheric ice water content (IWC), which accounted for only 20 % of the observed values. The interactive dust simulation with COSMO-MUSCAT, including a two-moment bulk microphysics scheme and dust–cloud as well as dust–radiation feedback, in contrast, led to significant improvements. The modeled cirrus cloud cover and IWC were by at least a factor of 2 higher in the relevant altitudes compared to the noninteractive model run. We attributed these improvements mainly to enhanced deposition freezing in response to the high mineral dust concentrations. This was corroborated further in a significant decrease in ice particle radii towards more realistic values, compared to in situ measurements from the ML-CIRRUS aircraft campaign. By testing different empirical ice nucleation parameterizations, we further demonstrate that remaining uncertainties in the ice-nucleating properties of mineral dust affect the model performance at least as significantly as including the online representation of the mineral dust distribution. Dust–radiation interactions played a secondary role for cirrus cloud formation, but contributed to a more realistic representation of precipitation by suppressing moist convection in southern Germany. In addition, a too-low specific humidity in the 7 to 10 km altitude range in the boundary conditions was identified as one of the main reasons for misrepresentation of cirrus clouds in this model study.

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